Tamper-proof axial tumbler lock



Nov. 24, 1970 w. J. KERR 3,54

I TAMPERPROOF AXIAL TUMBLER LOCK.

Filed Aug. 5, 1968 3,Sheets-Sheet 1 1-68 {a 26 INVENTOR 6 2 W 4- Attorney Nov. 24, 1970 w. J. KERR 3553, 9-

TAMPER-PROOF AXIAL TUMBLER LOCK Filed Aug. 5, 1968 3 Sheets-Sheet z.

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INVENTOR WILLIAM J. KERR Attorney W. J. KERR TAMPER-PROOF AXIAL TUMBLER LOCK Nov. 24, 1910 3,541,819

Fil ed Aug. 5, 1968 v 3 Sheets-Sheet a 9k 0.. m 3 |8 42 40 l6 l2 I4 38 50 FIG; 9

12 50 FIG. IO 2A8 3e. 4 r 38 5o 2 'qllllllr U1 A L Q x .\.m v. s. 32 I6 34 l2 I4 30 l8 FIG. I 28 64 36 I8 we 40 I4 38 5o 52 208 INVENTOR WILL/AM J. KERR Attorney United States Patent O 3,541,819 TAMPER-PROOF AXIAL TUMBLER LOCK William J. Kerr, Glenview, Ill., assignor to Chicago Lock Co., Chicago, Ill., a corporation of Illinois Filed Aug. 5, 1968, Ser. No. 750,323 Int. Cl. E05b 27/08 US. Cl. 70-363 12 Claims ABSTRACT OF THE DISCLOSURE defeat or pick the lock, a false picking is attainedwherein only one of the rotatable plug parts is released for turning movement, the lock shaft being fixed to the other rotatable plug part so that it cannot be rotated by the picking tool.

PERTINENT PRIOR ART (United States Patents) Kerr, 3,270,538, Sept. 6, 166.

OTHER PRIOR ART OF INTEREST (United States Patents) Wilson, 2,655,808, Oct. 20, 1953; Martin, 3,149,487, Sept. 22, 1964; Kerr, 3,267,706, Aug. 23, 1966; Kerr, 3,320,783, May 23, 1967.

The present invention relates generally to locks and has particular reference to an axial tumbler type lock of the type wherein the various composite pin tumblers are arranged in an annular series around, and extend parallel to, the central longitudinal axis of the lock. In a lock of this type, the tumblers slide in bores and extend between and also into the stationary cylinder part of the lock and a rotatable lock part in the cylinder part. These tumblers are transversely divided or split and are adapted to be longitudinally or axially displaced by the proper key for the lock against the resistance of helical springs and in such a manner that their splits coincide with the abutting interfacial surfaces of the aforementioned stationary and rotatable parts of the lock. For that purpose, the key which controls the lock is provided with an annular series of shoulders which are engageable with the front ends of the split tumblers and the effective longitudinal placement of which is such that when the key is pushed all the way to its home position within the lock cylinder, the splits of the tumblers will coincide with the aforementioned interfacial surfaces between the stationary and rotatable parts of the lock, thus permitting the rotatable lock part to be turned by the proper key. Locks of the type or character under consideration have for many years been manufactured and sold by Chicago Lock Co. of Chicago, Ill. under the trade name Ace.

There are at the present time a number of picking tools which are ostensibly for use by locksmiths but which are designed specifically for the purpose of defeating or picking Ace locks. These toools can be operated with varying degrees of skill to open such locks when the keys therefor have been lost or stolen. One such picking tool is shown and described in previously cited US. Pat. No. 3,149,487. Another picking tool for the same purpose is disclosed in and forms the subject matter of US. Pat. No.

, 3,541,819 Patented Nov. 24, 1970 "ice 2,655,808, also previously cited. Other picking tools which are capable of opening Ace locks have been developed from time to time both by authorized and unauthorized sources.

Picking tools which are capable of opening Ace locks are structurally and functionallly similar in that each of them includes a shank which, by means of a handle, may be manipulated so that tumbler-engaging fingers which are arranged in an annular series around the shank, conform to the arrangement of the tumblers of the lock to be opened and are under light frictional drag, are initially caused to enter into the front end of the lock in order to engage and rearwardly depress the split pin tumblers against the bias of their respective helical springs. The handle may then be placed under a manual rotational bias or torque in the direction of lock opening and reciprocated in and out, i.e., longitudinally of the lock, while at the same time the operator of the tool gradually withdraws the tool from the lock. During such jiggling of the tool, the split tumblers gradually slide forwardly. Because of the wide tolerances which are ordinarily maintained in the manufacture of the lock parts, the rotational bias which is applied to the tool causes a slight misalignment of the bores in the stationary and rotatable parts of the lock, thus presenting at the inner ends of the bores in the rotating part shoulders upon which the front ends of the tumbler sections in the stationary lock part may come to rest when the splits of the tumblers coincide wih the abutting end or interfacial surfaces of the stationary and rotating lock parts. As a result, the dividing lines or splits of the pin tumblers gradually become aligned with said interfacial surfaces between the stationary and rotatable lock parts. When all of the dividing lines or splits of the tumblers become aligned with the aforementioned interfacial surfaces, the rotatable part is released for rotation and the lock may then be opened, the opening thereof being an automatic one by reason of the constant rotational bias or torque which is maintained by the tool operator upon the handle of the picking tool.

During such a lock picking operation, the aforementioned tumbler-engaging fingers of the picking tool retract to different eudwise positions according to the lengths of the tumblers and they may be locked or otherwise held in such positions to provide a coded pattern for production of one or more duplicate keys for the picked lock.

While the manufacturer of Ace locks has no objection to possession of such lock picking tools by locksmiths and other authorized persons, it occasionally happens that such tools fall into the hands of unauthorized persons who use the same in an illicit manner to pilfer vending and other machines which are equipped with Ace type locks. At the risk of depriving authorized personnel from enjoying the benefits of possession of such lock-picking tools, it is the principal object of the present invention to provide a novel axial tumbler lock which may not be opened by means of lock picking tools similar to those of the two afore-mentioned United States patents.

Various means have heretofore been devised in an effort to prevent picking of Ace type locks, such means invariably involving modifications of the locks in such a manner that renders manipulation of the picking tools more diflicult and, therefore, imposes upon the tool operators special skills. While such so-called tamper or pick-proof Ace type locks very materially increase the length of time it requires a skilled operator to defeat or pick a given lock, they are not necessarily foolproof, and with a little practice coupled with patience, these locks can be defeated by picking.

The particular lock constituting the present invention differs from present day tamper-proof locks of the Ace type in that instead of rendering manipulation of the picking tool more difficult, it actually invites picking of the lock to the extent necessary to release the rotatable part of the lock for turning movement with respect to the non-rotatable or stationary part. Then, according to the invention, after the operator has, by exerting the previously described jiggling action on the picking tool, effected release of the rotatable part, he will find that rotation of such part does not effect rotation of the lock bolt which carries the locking cam and that his picking manipulations, although successful to release the rotatable part, affords him only an idle rotation which accomplishes nothing so far as lock opening is concerned. This idle rotation may, under certain circumstances, be a continuous one in either direction, or it may be a possible rotation through a few degrees as limited by a stop which may be provided to prevent interchange or tumbler parts between adjacent longitudinal tumbler-re ceiving bores, all in a manner that will become clear presently when the nature of the invention is better understood.

The provision of a tamper-proof lock of the character briefly outlined above constitutes the principal object of the present invention and it is a further object to provide an improved Ace type lock which does not differ appreciably either in size or shape, i.e., design, from a conventional Ace type lock and which, furthermore, occasions no change whatsoever in the design of the key which operates it. Because of this, the familiar outward appearance of the lock and key, insofar as the present invention is concerned, is preserved.

Other objects and advantages of the invention, not at this time enumerated will become readily apparent from a consideration of the following description.

The invention consists in the several novel features hereinafter set forth and more particularly defined by claims at the conclusion hereof.

In the accompanying three sheets of drawings forming a part of this specification, one illustrative embodiment of the invention is shown.

FIG. 1 is a perspective view of a key which is expressly designed for cooperation and use with the particular tamper-proof lock constituting the present invention;

FIG. 2 is a front perspective view of the lock;

FIG. 3 is a front elevational view of the lock:

FIG. 4 is a transverse sectional view taken on the lines 44 of FIG. 2;

FIG. 5 is an enlarged sectional view taken centrally and longitudinally through the lock, the view being on K the line 55 of FIG. 3 and showing the key operationally inserted in the lock;

FIG. 6 is a sectional view taken on the line 66 of FIG. 5;

FIG. 7 is a sectional view taken on the line 77 of i FIG. 5;

FIG. 8 is a sectional view similar to FIG. 5 but showthe key removed from the look so that the parts of the latter assume their normal positions;

FIGS. 9, 10, 11, 12 and 13 are fragmentary longitudinal sectional views, largely schematic in their disclosure, illustrating specifically a special ball and pin tumbler employed in connection with the present invention and further disclosing its functional cooperation with the rotatable and non-rotatable lock parts in which it is contained;

FIG. 14 is a side elevational view of a lock picking tool of conventional construction, the present invention being specifically designed to defeat the function of such picking tool; and

FIG. 15 is a fragmentary sectional view, schematic in its representation, illustrating a phenomenon associated with a conventional Ace type lock and by means of which the effectiveness of the picking tool of FIG. 14 is predicated.

Referring now to the drawings in detail and in particular to FIGS. 1 to 8, inclusive, the tamper-proof lock of the present invention is designated in its entirety by the reference numeral 10 and it comprises an outer stationary lock cylinder 12 within which there is disposed a three-part plug assembly consisting of a fixed or stationary rear part 14, a contiguous rotatable intermediate part 16, and a rotatable front part 18 which, prior to insertion of a key into the lock, normally remains spaced a slight distance in front of the intermediate part 16. The fixed rear part 14 is maintained within the rear end region of the cylinder 12 against rotation by means of a drive-fit pin 20 which extends radially through the rear end region of the cylinder and has its inner end projecting into a correspondingly shaped socket 21 in the fixed rear part. The rotatable front part 18 and the fixed rear part 14 are of annular or sleevelike construction, while the rotatable intermediate part 16 is provided with an integral, rearwardly extending, reduced shank 22 which constitutes the lock shaft and extends not only through the fixed rear part 14 but also beyond the axial extent of the lock cylinder 12. This projecting rear end portion of the shank is provided with an external screw thread 24 and receives thereover a pair of spaced apart clamping nuts 26 by means of which the usual radial locking bolt 27 is held in position on the lock shaft.

Seven four-part ball-and-pin split tumblers are arranged in an annular series about the central longitudinal axis of the lock cylinder 12. These composite or split tumblers are shown in detail in FIGS. 9 to 13, inclusive, and are designated at 28 by means of brackets in these five views. The tumblers 28 are slidable longitudinally in respective bores 30, 32 and 34 in the three plug parts 14, 18 and 16. The bores 30 are in the form of blind bores or spring retainer sockets.

Each composite tumbler 28 consists of a rectilinear series of four elements including a front tumbler pin 36, a rear tumbler pin 38, an intermediate tumbler pin 40, and a tumbler ball 42, the latter being interposed between the front and intermediate tumbler pins. The front tumbler pin 36 slides for the most part in the bore 32. The intermediate tumbler pin slides for the most part in the bore 34. The rear tumbler pin slides for the most part in the bore 30. The tumbler ball 42 rides'in the vicinity of the opposed surfaces which exist between the front and inter mediate plug parts 18 and 16 and is of a diameter slightly greater than the Width of the void which separates these two plug parts.

In the unlocked position of the look after the proper key has been introduced into the front end of the lock cylinder 12, the key forces the front plug part 18 rearwardly in a manner that will be described presently and the tumbler ball 42 is intersected substantially centrally by the interfacial surfaces which then exist between the plug parts 18 and 16 as shown in FIGS. 8 and 11, while at the same time the split which is established by the meeting or abutting ends of the tumbler pins 38 and 40 lies on the interfacial surfaces between the plug parts 16 and 14 with the result that the ball 42 establishes a driving connection between the two rotatable plug parts and, consequently, such parts may be rotated in unison to actuate the locking bolt 27 in the usual manner of an Ace type ock.

It will be understood, of course, that as is customary in connection With an Ace type lock, the various tumbler pins will be cut to varying lengths so that in the normal position of the lock parts before the key is inserted into the cylinder 12, certain of the tumbler pins will project across the interfacial surfaces between the adjacent plug parts while the tumbler ball 42, in such in stances, may lie wholly within either the front plug part 18 or the intermediate plug part 16.

As best illustrated in FIGS. 9 to 13, inclusive, the various composite or split tumblers 28 are yieldingly urged forwardly in the respective bores which enclose them and, accordingly, the rear tumbler pin 38 of each com posite tumbler is provided with a rearwardly extending pilot stem 50 which is surrounded by a helical compression spring 52, the rear end of the latter bearing against the bottom of the associated blind bore or socket 30.

The lock cylinder 12 is provided at its front end with an enlarged head portion 60 having an inwardly extending annular flange 62. The latter constitutes a protective plate and embodies a central circular opening 64 through which the shank portion of the lock key is adapted to be projected when it is inserted into the front end of the lock cylinder for locking or unlocking purposes. An inwardly extending notch 65 in the flange 62 insures proper placement of the key shank in the opening 64. A dual pilot member 66 projects through the annular barrel part 16 and embodies a relatively thick front pilot post 68 for the hollow shank of the lock key, and in addition, a relatively thin rear pilot post 70 which extends into a cylindrical socket 72 in the intermediate plug part 16 and serves to maintain the front and intermediate plug parts in axial alignment during and after lock assembly operations. The front pilot post 68 is formed with a longitudinally extending notch 74 (see FIGS. 2, 3, 4 and 5) designed for cooperation in the usual manner of lock and key operation with a counterpart guide lug provided internally of the hollow key shank, all in a manner that will be described after the nature of the lock key has been set forth.

The inner or rear face of the front plug part 16 is formed with a peripheral clearance notch 80 (see FIGS. 5, 6 and 8) of small circumferential extent and on the order of 12. This notch is designed for cooperation with a longitudinally extending plunger or limit pin 82 (see FIGS. 5 and 7) which slides in a socket 84 in the intermediate plug part 16 and is urged forwards by way of a helical compression spring 86 so that it projects forwardly from the front face of the intermediate plug part 16 and serves, in conjunction with the notch 80, the dual purpose of limiting the extent of relative turning movement of which the two plug parts 16 and 18 are capable, and also of yieldingly biasing the front plug part 18 forwardly to its normal position as shown in FIGS. 8 and 13 of the drawings. It is not essential that the two plug parts 16 and 18 be thus limited in their relative motion but, when they are so limited, certain advantageous features which will subsequently be set forth in detail are attained.

A proper key for the lock is illustrated in detail in FIG. 1 and is designated in its entirety by the reference numeral 100. This key is similar to a conventional key for operating a standard Ace lock and it includes a cylindrical body portion or shank 102 to one end of which there is fixedly secured a manipulating wing-type handle 104. The shank 102 is tubular and the forward rim thereof is notched at seven circumferentially spaced regions therearound so as to provide a series of forwardly facing, tumbler-engaging shoulders 106 which, when the shank is telescopically received over the pilot post 68 of the dual pilot member 66 of the lock 10, engage the front ends of the front tumbler pins 36 and depress the various composite tumblers 28 against the biasing action of their respective springs 52. An internal lug 108 on the forward rim of the key shank 102 cooperates with the aforementioned notch 74 in the pilot post to assure proper placement of the key shank on the post so that the various forwardly facing shoulders 106 will register with the proper tumblers 28 for which they are designed. An external lug 110 on the forward rim of the shank cooperates with the aforementioned notch 65 (see FIG. 3) to assure proper placement of the key shank in the central opening 64 so that the shank may enter the lock cylinder only when the notch 65 and the groove 74 are in register.

The lock 10 is adapted to be installed upon a door or other structure (not shown), the lock cylinder 12 passing through a suitable hole or opening (also not shown) in 6 the door and the cylinder being fixedly held in position by a nut 112 (see FIG. 5) which serves to clamp the annular rear end face of the enlarged head portion 60 of the cylinder hard against the forward side of the door or other structure.

In the normal operation of the herein described lock 10, utilizing a proper key such as the key 100, when the key shank 102 is inserted through the central opening 64 of the lock cylinder 12 in the manner previously described, the forward circular rim of the tubular body portion or shank 102 of the key will engage the front face of the front plug part 18 and force the same rearwardly into interfacial contact with the intermediate plug part 16 as shown in FIG. 5. Thereafter, the various forwardly facing shoulders 106 will engage the forward ends of the front tumbler pins 36 with which they are aligned and the composite tumblers 28 will be shifted rearwardly in their respective sets of aligned bores 30, 32, 34 to such an extent that the tumbler balls 42 will intersect the interfacial surfaces between the then abutting plug parts 18 and 16 as shown in FIG. 11. At the same time, the splits which exists between the adjacent tumbler pins 38 and 40 will be positioned at the interfacial surfaces between the adjacent plug parts 16 and 14. With the various tumbler parts or elements thus positioned, the various tumbler balls 42 will establish a driving connection between the plug parts 18 and 16 so that these two parts may be turned in unison under the influence of the key which drives the dual pilot member 66 by reason of the interlocking arrangement of the lug 108 and the notch 74. The dual pilot member '66 is press-fitted into the rotatable annular front plug part 18 so that the torque which is applied to the key 100 is transmitted through the dual pilot member 66 to the front plug part 18, and from thence through the tumbler balls 42 to the intermediate plug part 16 and, consequently, to the locking bolt 27. It is to be noted at this point that the interfacial surfaces between the plug parts 18 and 16 intersect the tumbler balls 42 in a manner which substantially bisects these tumbler balls. Under the circumstances, there is little tendency for the balls to shift longitudinally in the respective bores in which they are mounted and, therefore, the drive from the front plug part 18 to the intermediate plug part 16 is a positive one. The various springs 52 on the one hand and the depressive action of thevarious shoulders 106 on the key 100 inhibit any tendency for the balls to shift longitudinally in either direction, even if, due to an error in manufacturing tolerances a given tumbler ball might be slightly displaced from its centered position with respect to the aforementioned interfacial surfaces between the plug parts 18 and 16. Upon withdrawal of the key 100 from the lock cylinder 12, the spring 86, acting through the plunger or limit pin 82, forces the front plug part 18 forwardly, thus reestablishing the gap between the intermediate and front plug parts 16 and 18 so that the various lock parts are restored to the positions in which they are shown in FIGS. 8 and 13.

Considering now the tamper-proof features of the present lock 10, the lock is immune to any attempt to defeat or pick it by utilizing any of the various commercial or other picking tools which have been devised in an effort to pick conventional Ace type looks. The most commonly used picking tool for use in connection with Ace locks constitutes the subject matter of heretofore cited US. Pat. No. 3,149,487, and the entire disclosure of such patent, insofar as it is pertinent to the present invention is, by reference, hereby incorporated in and made a part of this specifification. However, for convenience, such a picking tool is disclosed in FIG. 14, and in FIG. 15 a phenomenon that is associated with conventional Ace locks whereby such a picking tool is effective is schematically illustrated.

The picking tool of FIG. 14 is designated in its entirety by the reference numeral 200 and it embodies a tubular shank 202 which carries a handle 204 at its front end and has an annular series of longitudinally extending grooves 206 in its outer cylindrical surface. Each of the grooves has longitudinally slidable therein a tumblerengaging finger 208 and all of the fingers are held in position within their respective grooves by means of one or more bands 210 of rubber or other elastomeric material. The rear or left-hand end region of the shank is formed with a reduced diameter section 212 which defines a rearwardly facing annular shoulder 214, the reduced section being of such diameter that it may enter the annular lock opening of a standard Ace lock or the lock opening 64 of the present lock 10 to the extent permitted by the shoulder 214. The front ends of the fingers 208 are turned outwardly as shown at 216 for individual manipulation of the fingers, and a fiat washerlike ring 218 loosely surrounds the shank 202 near the handle 204 and forwardly of the fingers 208 for collective manipulation of the latter in a manner that will be made clear presently.

The number and disposition of the slidable tumblerengaging fingers 208 correspond to the number and disposition of the composite tumblers 28 of the lock 10 so that when the reduced section 212 of the shank 202 is inserted in the central circular lock opening 64, the rear ends of the fingers will engage the front ends of the split tumblers, thus shifting the tumblers rearwardly in the lock 10. The reduced diameter section 212 of the picking tool shank 202 is formed with an outwardly extending radial lug 220 which enters the notch 65 in the enlarged head portion of the cylinder 12 of the lock 10 when the tool 200 is applied to the lock and by means of which the various fingers 208 are constrained to become aligned with their respective tumblers 28 during an attempt to manipulate or operate the tool.

When the picking tool 200 is applied to a conventional Ace lock in an attempt to defeat or pick the same, the various fingers 208 are caused to project rearwardly beyond the rear end of the tubular shank 202 so that they overhang the shoulder 214 and assume similar longitudinal positions with respect to the shank 202. Thus, when the shank is projected into the central opening of a standard Ace lock, all of the split tumblers of the lock will be shifted rearwardly so that the splits associated therewith lie rearwardly of the interfacial surfaces which exist between the rotatable and the non-rotatable plug parts of the lock.

For a detailed understanding of the manner in which the tool 200 is manipulated after it has thus been introduced into the central opening of a conventional Ace lock, reference may be had to US. Pat. No. 3,270,538,

but it is believed adequate for descriptive purposes herein to state that by slowly withdrawing the shank portion of the tool, utilizing a fore-and-aft jiggling motion and maintaining a clockwise angular bias on the tool, the spring-biased split tumblers overcome the coefficient of running friction presented by the rubber bands 210 against the fingers 208 so that the split tumblers gradually slide forwards. The rotational bias or torque that is maintained upon the rotatable plug part of the lock effects a slight misalignment of the bores associated with this rotatable part and the fixed part, such a misalignment being illustrated in FIG. 15 wherein a fragment of a standard Ace lock is illustrated. In this view, the lock cylinder 310 encloses a rotatable plug part 312 having a tumbler-receiving bore 314 therein, and a fixed plug part 316 having a bore 318 therein. It is to be considered that the front tumbler section 320 and the rear tumbler section 322 have been slid forwards under the biasing action of the helical compression spring 324 working against one of the fingers 208 on the picking tool 200 until such time as the rear tumbler section has caught, so to speak, on the overhanging edge of the bore 314, all in the manner as specifically set forth in previously mentioned US. Pat. No. 3,270,538. When such a condition obtains in connection with all of the seven split tumblers that are associated with 8 the conventional lock of FIG. 15, the rotational bias that is applied to the rotatable plug part 312 effects the desired turning movement of such plug part to its unlocked posi tion.

Considering now an attempted application of the picking tool 200 to the present tamper-proof lock 10, when the tubular shank 202 is initially inserted into the central opening 64 of the lock cylinder 12 and pushed forwardly in the direction of the lock as a whole, the forward rim of the picking tool shank 202 engages the front plug part 18 and shifts it rearwardly against the intermediate plug part 16 in a manner similar to that which obtains when the proper key for the lock is inserted in the lock cylinder 12. At this time, the several tumbler-engaging fingers 208 of the tool engage and depress their respective composite tumblers 28 so that all of the front tumbler pins 36 project beyond the interfacial surfaces which exist between the front plug part 18 and the intermediate plug part 16 after the two parts have been closed upon each other by the forward pressure of the tool shank 202. At the same time, all of the tumbler balls 42 shift into the intermediate plug part 16.

Such a condition is illustrated in FIG. 12, only one exemplary composite tumbler being illustrated. Because of the fact that the front tumbler pin 36 crosses the interfacial surfaces between the plug parts 18 and 16, no relative turning movement between these two parts is possible. Similarly, because of the fact that the intermediate tumbler pin 40 crosses the interfacial surfaces between the plug parts 16 and 14, no relative turning movement between the interlocked plug parts 18, 16 and the fixed plug part 14 can take place.

Considering now that the picking tool 200 is manipulated in its intended manner by jiggling the same in a fore-and-aft direction as previously described, the force exerted by the various helical compression springs 52 will cause a collective rearward movement of the entire set of composite tumblers 28 substantially in the manner which occurs when the picking tool is used in connection with a standard or conventional Ace lock. As each composite tumbler 28 progressively moves rearwardly, the tumbler ball 42 thereof approaches and ultimately arrives at the position illustrated in FIG. 10 wherein the interfacial surfaces between the plug parts 18 and 16 extend tangentially with respect to the tumbler ball 42 while the front tumbler pin 36 is wholly disposed within the front plug part 18. At this particular point, said plug part 18 is free to turn with respect to the intermediate plug part 16 insofar as the particular involved tumbler 28 is concerned. The slight misalignment between the bores 32 and 34 which exists due to manufacturing tolerances and the fact that a constant rotational bias is applied by the picking tool to the front plug part 18, serves to block further rearward movement of the ball 42 so that the tumbler ball 42, the intermediate tumbler plug 40 and the rear tumbler pin 38 are held in check while others of the various composite tumblers 28 approach and ultimately assume the same relative positions with respect to the interfacial surfaces between the plug parts 18 and 16. When all of the composite tumblers 28 assume the condition illustrated in FIG. 10, the front plug part 18 is free to turn with respect to the intermediate plug part 16 and, in so turning, all of the tumbler balls 42 are cammed slightly rearwardly so that they ride upon the rear end face of the front plug part 18, this latter plug part thus being released from its interlocking engagement with the intermediate plug part 16. Insofar as the action of the picking tool 200 is concerned, at this point the tool has been manipulated only to release the interlock between the front pug part 18 and the itermediate plug part 16, but it has not been successfully manipulated to release the interlock between the rotatable intermediate plug part 16 and the fixed rear plug part 14, such parts remaining interlocked by reason of the bridging action of the rear tumbler pins 38. Stated otherwise, a false picking of the lock has been attained wherein the front plug part 18 may rotate while the intermedaite plug part 16 and the rear plug part 14 remain fixed and locked to each other. The locking bolt 27 is thus not affected and remains in its locking position.

It has been found that this false picking of the lock by means of the picking tool 200 is more readily attained and with considerably less manipulative skill than is involved in connection with the picking of a standard Ace lock. For this reason, it may b aptly stated that the present lock invites picking of the lock but the only interlock release which can be attained is that which exists between the front and intermediate plug parts 18 and 16.

If desired, and according to the present invention, after the lock 10 has been falsely picked as previously described, the front plug part 18 may be allowed to rotate continuously throughout a full 360 turn if desired, but it has been found expedient to limit the extent of rotational movement thereof by means of the previously described pin and notch connection (82, 80) which is shown in FIG. 6. As soon as the front plug part 18 is released for turning movement with respect to the intermediate plug part 16, the lost motion existing in the aforementioned pin and notch connection is taken up so that only a few degrees of turning movement of the front plug part is permitted. The pin and notch connection (82, 80) is desirable in order to prevent possible loss of a given tumbler ball 42 from one composite bore 30, 32, 34 and its transfer to an adjacent bore during manipulation of the picking tool 200 in the lock 10. Successful or eifective manipulation of the picking tool is not an exact procedure and the false picking of the lock 10 as previously described may sometimes be attained when one or more of the tumbler balls 42 has slipped rearwardly past the interfacial surfaces which exist between the front and intermediate plug parts 18, 16 so that the position illustrated in FIG. 9 is assumed. The front plug part 18 still is released from the intermediate plug part 16 and rotation of the former part 18 will carry the ball 42 into alignment with the next adjacent composite bore and in longitudinal alignment with the tumbler ball 42 already positioned in such bore so that the spring 52 may force both balls into the same bore. Under such a circumstance, the lock may not be restored to its normal condition except by dismantling the same and individually and properly relocating the various parts thereof. The extent of lost motion that is afforded by said pin and slot connection (82, 80) is less than the circumferential distance between any two adjacent bores 32 to prevent such multiple piling of tumbler balls in the same bore.

It is to be noted at this point that even if a given picking tool 200 is adjusted to correspond exactly to the shoulder placement or position of the proper key for the lock 10, the tool will not operate to obtain a true picking of the lock and will function only to obtain the false picking heretofore described. This is because with the proper key 100, the shoulders 106 are all fixed against longitudinal displacement with respect to one another, while in the case of the picking tool 200, the shoulders that are afforded by the tumbler-engaging fingers 208 are yieldable under the sliding action that is permitted by the rubber bands 210. With the proper key, therefore, the various composite tumblers 28 of the lock 10 are fixedly held in their lock opening positions when the key is inserted into the lock cylinder 12. With the picking tool 200, they are not so held and the operator is given no indica' tion that the time has arrived when any given tumblerengaging finger 208 should be secured in its position of plug release wherein the front and intermediate plug parts 18 and 16 are effectively interlocked by the tumbler balls 42 and the two plug parts 16 and 14 are released from their interlock by the existence of the splits which are cre' ated by the abutting ends of the tumbler pins 38 and 40 as shown in FIG. 9.

In the schematic disclosure that is represented by FIGS. 9 to 13, inclusive, FIG. 13 illustrates the normal position of the illustrated composite tumbler 28 before either the proper key 100 or the picking tool 200 is inserted into the lock cylinder 12. The plug parts 18 and 16 are interlocked by the intermediate tumbler pin 16 of the illustrated tumbler 28 and the plug parts 16 and 14 are interlocked by the rear tumbler pin 38 so that the lock shaft 22 and the locking bolt 27 may not be shifted. As previously described, FIG. 11 represents the position of the illustrated composite tumbler 28 when the proper key is inserted into the lock cylinder so that the tumbler ball 42 establishes a drive between the plug parts 18 and 16 while the plug parts 16 and 14 are released from each other.

FIG. 12 represents a condition Where the shank portion 202 of the picking tool 200 has pushed the front plug part 18 rearwards against the intermediate plug part 16 and wherein one of the tumbler-engaging fingers 208 of the tool has initially depressed one of the composite tumblers 28 to its fullest extent so that the front tumbler pin 36 establishes an interlock between the plug parts 18 and 16, while the intermediate tumbler pin 40 establishes an interlock between the plug parts 16 and 14. In this case, no turning of any of the three plug parts is possible.

FIG. 10 represents a condition where the picking tool has been manipulated so that a false picking of the lock is attained wherein the front plug part 18 is released from its interlocking rotational engagement with the intermediate plug part 1 6 but in Which the intermediate plug part 16 remains interlocked with the fixed rear plug part 14 by the intervening intermediate tumbler pin 40.

FIG. 9 represents a special condition wherein one of the tumbler-engaging fingers 208 of the picking tool has been allowed, through slippage thereof, to move into the forward bore 32, the two plug parts 18 and 16 being released from each other so that, in the absence of the lost motion connection that is aiforded by the pin and slot con nection 82, (see FIG. 6), the tumbler ball 42 is capable of being transferred from one composite bore 30, 32 and 34 to the next adjacent circumferentially spaced bore.

It is to be noted at this point that because the diameter of the tumbler balls 42 is greater than the maximum longitudinal extent or width of the void which becomes established between the front plug part 18 and the intermediate plug part 16 as shown in FIG. 13, there is no opportunity for any of these balls to enter this void and become lodged between these two plug parts.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. For example, it is within the intent of the present invention to dispense with the spring-biasing feature that is associated with the plunger or limit pin 82 and fixedly to secure this limit pin to the intermediate plug part 16 in such a manner that the front plug part 18 at all times bears against the intermediate plug part 16 regardless of whether the key is disposed in the lock cylinder 11 or removed therefrom. Under such a condition, the limit pin 82 will serve solely to limit the relative rotation between the front plug part 18 and the intermediate plug part 1-6 to an angular rotation of approximately 12 as previously stated. However, when the limit pin 82 is spring-biased in the manner described herein, manipulation of the lock picking tool 200 is made increasingly difficult due to the fact that each time an increment of forward withdrawal movement is applied thereto, the front plug part 18 will follow this withdrawal movement and open the gap which exists between the front plug part 18 and the intermediate plug part 16 as shown in FIG. 13, in which case the chances for attaining a false picking of the lock by release of the front plug part 18 from the intermediate plug part 16 are greatly enhanced.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. In an axial tumbler lock, in combination, a lock cylinder, a three-part lock plug disposed in said cylinder and including a fixed rear part, a rotatable front part, and a rotatable intermediate part, adjacent parts presenting planar running faces, a lock shaft carried by said intermediate part and projecting rearwardly of the cylinder, a series of normally aligned longitudinal bores in said parts and movable into and out of such alignment, and a four-part tumbler slidable in said aligned bores and including first, second, third, and fourthtumbler elements extending from front to rear in the order named, said second tumbler element being in the form of a spherical ball, spring means yieldingly urging said tumbler forwardly in said aligned bores, the tumbler in the normal unlocked condition of the lock having its first and second elements effectively disposed in the front plug part, its third element extending between the front and intermediate plug parts and effecting an interlock therebetween, and its fourth element extending between the intermediate and fixed rear plug parts and effecting an interlock therebetween, and a key having tumbler-engaging shoulders which are effective when the key is operatively received in the lock cylinder to shift said tumbler to a position wherein the second element establishes a driving connection between the front and intermediate plug parts, the second element is substantially intersected by the interfacial running surfaces existing between the front and intermediate plug parts, the third element is substantially wholly disposed within the intermediate plug part, and the fourth element is withdrawn from the intermediate plug part, thus releasing the first and second plug parts for rotation in unison.

2. In an axial tumbler lock, the combination set forth in claim 1 and wherein the plug parts are provided with additional and similar series of normally aligned longitudinal bores, additional and similar tumblers slidable in said bores, said series of aligned bores being circumferentially spaced around the axis of the plug with substantially equal spacing between adjacent series of bores, there being an interlocking lost motion connection between the front plug part and the intermediate plug part and effective to limit the rotational movement of the front plug part with respect to the intermediate plug part to an angular displacement which is less than the angular displacement of each series of bores from the next adjacent series of bores.

3. In an axial tumbler lock, the combination set forth in claim 2 and wherein said lost motion connection between the front and intermediate plug parts comprises a pin on one of said parts and a notch in the other part into which said pin projects.

4. In an axial tumbler lock, the combination set forth in claim 3 and wherein the pin is carried by the intermediate plug part and projects loosely into said notch.

5. In an axial tumbler lock, the combination set forth in claim 1 and wherein the lock shaft is in the form of a rearwardly extending reduced shank which is integrally formed on the intermediate plug part and projects completely and rearwardly through said fixed rear plug part.

6. In an axial tumbler lock, the combination set forth in claim 5 and wherein the front plug part is provided with a pilot post which projects into a socket in the in termediate plug part.

7. In an axial tumbler lock, the combination set forth in claim 5 and wherein the front plug part is provided with a rear pilot post which projects into a socket in the intermediate plug part, and with a front 12 pilot post, said key being provided with a tubular shank on which said tumbler-engaging shoulders are formed and which is telescopically receivable over said front pilot post.

8. In an axial tumbler lock, the combination set forth in claim 7 and wherein the front and rear pilot posts are integral and are in the form of a dual pilot member which projects completely through the front plug part centrally thereof and is press-fitted therein.

9. An axial tumbler type lock comprising a lock cylinder, a three-part plug disposed within the cylinder and including a first non-rotatable part and second and third independently rotatable parts, said parts being coaxial, a composite axially shiftable split tumbler projecting through said third and second plug parts and extending into the first plug part, said tu-rnbler being effective in one position thereof to maintain all of said plug parts against relative rotation, in another position thereof to maintain said first and second parts against relative rotation while releasing the third plug part for independent rotation, and in a third position to maintain said third and second plug parts against relative rotation while releasing said second plug part for rotation in unison with said third plug part, and a locking elementmovable in unison with said second plug part, said first and second plug parts being disposed in contiguity against axial shifting within the cylinder and providing a common planar interface, said third part being axially shiftable between a retracted position wherein it is spaced forwardly from the second plug part and an advanced position wherein it is in contiguity with said second .plug part so as to establish a common planar interface therewith, and spring means yieldingly urging said third plug part toward its retracted position.

10. An axial tumbler type lock as set forth in claim 9, and wherein said spring means comprises an extensible limit pin effectively interposed between the second and third plug parts, slidably disposed in one of said two latter parts, and bearing against the other part.

11. An axial tumbler type lock as set forth in claim 10 and wherein the second plug part is formed with a socket therein, the limit pin being slidable in said socket and projecting forwardly therefrom with its forward end bearing against the third plug part.

12. An axial tumbler type look as set forth in claim 11 wherein said third plug part is provided with a recess having a circumferential extent on the order of 12 and wherein the forward end of the limit pin projects loosely into said recess and bears against the bottom wall thereof, thereby limiting the extent of relative turning movement between the third and second parts.

References Cited UNITED STATES PATENTS 1,718,130 6/1929 Frischmuth 363 3,411,311 11/1968 Schlage 70363 FOREIGN PATENTS 532,372 8/1955 Italy.

MARVIN A. CHAMPION, Primary Examiner R. L. WOLFE, Assistant Examiner U.S. Cl. X.R. 

